The Environmental Protection Agency (EPA) requires vehicle manufacturers to install on-board diagnostic (OBD) systems for emission control on their light-duty automobiles and trucks beginning with model year 1996. OBD systems typically monitor vehicle emission control systems to detect any malfunction or deterioration that may cause emissions to exceed certain thresholds, such as state-mandated emission requirements or other thresholds. In conventional OBD systems, all (or substantially all) information monitored and/or calculated by an OBD system may be made available through a standardized, serial 16 cavity connector referred to as a Data Link Connector (DLC). The physical and electrical characteristics of typical DLCs provided on vehicles may be standard for all vehicles sold in the United States after 1996.
Generally, a variety of vehicle functions may be monitored by a vehicle's OBD system and, based on observed irregularities in the monitored functions, the OBD system may set one or more “trouble codes” that indicate a specific mechanical or electrical problem with the vehicle (e.g., an emission threshold has been exceeded). Via the DLC, the trouble codes currently set on the OBD may be accessed for any number of applications such as, for example, emissions testing, maintenance, repair diagnostics, or other applications. In some known diagnostic and testing systems, a vehicle testing/diagnostic system may be connected with the OBD to access the trouble codes. The vehicle testing/diagnostic system may be connected with the OBD by way of a serial 16 pin connector, or DLC, that corresponds to the serial 16 cavity DLC provided on the vehicle.
Known emission testing systems exist in which a vehicle may enter a testing station where a vehicle testing/diagnostic system may be connected via a DLC with an OBD system in the vehicle. Based on the trouble codes currently set in the OBD, the vehicle testing/diagnostic system may classify the vehicle as a “pass” or a “fail”. However, should the vehicle testing/diagnostic system be unable to communicate with the OBD upon connection due to a malfunction associated with the OBD system, or for other reasons, the vehicle may be classified as a “fail.” Some conventional emission testing systems may be incapable of detecting instances wherein a failure to communicate between the vehicle testing/diagnostic system and the OBD may be caused by a malfunction associated with the testing station (e.g., a faulty DLC associated with the vehicle testing/diagnostic system) rather than a malfunction associated with the OBD system. Consequently, in cases wherein a malfunction may be present at the testing station, vehicles may be incorrectly classified as “fails” with respect to meeting emissions standards. Similarly, known diagnostic systems may not be capable of determining instances in which a failure to communicate with an OBD system may be due to faulty diagnostic equipment, as opposed to a faulty OBD system. These and other drawbacks exist with conventional diagnostic and testing systems that communicate with OBD systems.